Fastener driving tool with improved valve

ABSTRACT

A snap-action valve for a fluid motor that includes a cylinder and a piston reciprocably mounted therein. The snap-action valve is located at the upper cylinder end and includes a diaphragm supported about its periphery with one surface facing the upper cylinder end and movable between a position spaced from that end and a position adjacent thereto. The diaphragm divides a housing into an upper chamber and a lower chamber, the latter continually provided with pressurized air. A resilient flat disc is secured at its center to the surface of the diaphragm facing the cylinder. A control valve admits pressurized air to the upper chamber to drive down the diaphragm to its cylinder-adjacent position against the force exerted by the pressurized lower chamber to carry the disc into sealing engagement with the cylinder end. After the control valve begins to release the upper chamber air, the pressurized air in the lower chamber moves the diaphragm upwardly away from the cylinder end but initially maintains the disc in sealing engagement with the cylinder. After a predetermined movement of the diaphragm, the disc snaps upwardly against the diaphragm back to its flat configuration to instantaneously provide a large opening at the upper cylinder end thereby minimizing the pressure drop of the high-pressure air being admitted into the cylinder. The pressurized air from the lower chamber upon entering the cylinder then drives down the piston, whereafter the control valve resupplies the upper chamber with pressurized air to again seal off the cylinder in preparation for subsequent cycles.

united States Patent [191 Wilson et a1.

[ FASTENER DRIVING TOOL WITH IMPROVED VALVE [76] Inventors: Steven J.Wilson, 1936 Orrington,

. Evanston, 111. 60201; Frank C.

Howard, 1646 Barberry Ln., Mt. Prospect, both of 111. 60056 [22] Filed:July 10, 1972 [21]. Appl. No.: 270,189

[52 us. or 227 13o, 251/61.1, 251/75,

251/25 [51] Int. Cl. B256 1/04 [58] Field of Search 251/25, 75, 61.1;91/417, 91/417 A, 461, 468; 173/169; 227/130 [56] References CitedUNITED STATES'PATENTS 2,713,165 7/1955 Campbell et a1 227/130 2,893,4167/1959 Hegstad 251/75 3,067,724 12/1962 Jenny et al 227/130 X 3,106,13610/1963 Langas et al 91/468 X 3,563,438 2/1971 Doyle et a1. .L 227/130 X3,608,574 9/1971 Beaussant... 251/6l.1 X

Primary Examinerl-lenry T.- Klinksiek Attorney, Agent, or FirmDressler,Goldsmith, Clement & Gordon, Ltd.

57 ABSTRACT A snap-action valve for a fluid motor that includes a 1 July9, 1974 cylinder and a piston reciprocably mounted therein. Thesnap-action valve is located at the upper cylinder end and includes adiaphragm supported about its periphery with one surface facing theupper cylinder end and movable between a position spaced from that endand a position adjacent thereto. The diaphragm divides a housing into anupper chamber and a lower chamber, the latter continually provided withpressurized air. A resilient flat disc is secured at its center to thesurface of the diaphragm facing the cylinder. A control valve admitspressurized air to the upper chamber to drive down the diaphragm to itscylinderadjacent position against the force exerted by the pressurizedlower chamber to carry the disc into sealing engagement with thecylinder end. After the control valve begins to release the upperchamber air, the

pressurized air in the lower chamber moves the diaration forsubsequentcycles.

8 Claims, 3 Drawing Figures I o TL WITH IMPROVED VALVE BACKGROUND OF THEINVENTION This invention relates to an improvement in fluiddriven motorsof the type including a piston reciprocable in a cylinder under theinfluence of pressurized fluid. More particularly, it relates to animproved valve for such a motor and an improved pneumaticallydrivenfastener driving tool utilizing an air-driven motor.

Fluid motor driven tools of many types, including pneumatic tools drivenby pressurized air, have received wide acceptance in the art. Forconvenience of FASTENER DlRI I description the following will beconfined to the pneumatic context, it being understood that theinvention is equally applicable to fluids other than air. A particularuseful example of such tools have been those utilized for drivingfasteners such as staples, T-nails, and the like, into relativelypierceable materials, one example being described in US. Pat. No.3,106,136 to A. Langas for Fastener Driving Tool, which patent isassigned to assignee of the present invention. To the extent that thedisclosure of this patent is not inconsistent with that of the presentinvention, it is incorporated by reference herein.

Although highly satisfactory, such tools have not utilized the storagefluid or air pressure driving the tool with maximum efficiency. It hasbeen found that the pressure of the air driving the piston of thepneumatic motor is lower than that of the pressurizedair before enteringthe cylinder. This condition is accentuated due to the relative slownesswith which even relatively fast acting valves of conventional designadmit pressuriz ed air to the cylinder. I

The substantial reduction of such a valve opening gradient must beachieved before optimum pressure transferral to the piston and animprovement in efficiency can be obtained.

- A fastener driving tool with such advantages would exhibit a distinctimprovement in speed of operation and driving force brought to bear onthe staple, nail, or other fastener.

SUMMARY OF THE INVENTION The present invention provides a novelsnap-acting valve assembly for controlling the flow of fluid underpressure into a chamber, particularly one containing a fluid motor. Thevalve comprises a valve support member movably supported adjacent anentrance to the chamber and having a first surface for closing thechamber and defining an area outwardly of the chamber exposed to thefluid under pressure. The valve support member also defines a secondsurface opposite the first surface. The first surface area is subjectedto a first force due to the fluid pressure tending to bias the firstsurface away from the entrance. The second surface is subjected to asecond force counteracting the first biasing force to bias the membertoward the entrance. This second biasing force may also be supplied bymeans of fluid pressure acting over the second surface.

Also included in the valve assembly is a flexible disc secured to thefirst support surface inwardly of at least one portion of the discperiphery whereby the disc is movable relative to the first supportsurface. The sup port member biases the disc into sealing engagementwith the chamber entrance while the second biasing 2 force opposes thefirst biasing force. When the first biasing force is reduced, however,the support member begins to move away from the chamber entrance. At thesame time the disc initially continues in sealed relationship with thechamber entrance under the influence of the pressurized fluid, whichthen flows between the disc and the first surface of the valve supportmember. The fluid pressure biases the periphery of the disc against thechamber entrance despite the movement of an inward portion of the discupwardly with the valve support member. Finally, the valve supportmember reaches a position spaced from the chamber entrance and the discfinally snaps away from the entrance against the first surface of thesupport member, thereby instantaneously opening a large aperture to thechamber entrance to allow the pressurized fluid to enter the chamberwithout the pressure loss normally occurring when the fluid enters achamber controlled by a conventional valve initially presenting a smallopening to the pressurized fluid. Thus, the full available air pressureis utilized by the fluid motor for a substantial improvement in thespeed of operation of the motor for a given fluid pressure, as well as asubstantial improvement in power and efficiency because of the fluidpressure conserved.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG. 1 is a sideelevational view showing a fastener- DETAILED DESCRIPTION While thisinvention is susceptible of embodiment in many different forms, there isshown in the drawings and will herein be described in detail a preferredembodiment of the invention with the understanding that the presentdisclosure is to be considered as an exemplification of the principlesof the invention and is not intended to limit the invention to theembodiments illustrated. The scope of the invention will be pointed outin the appended claims.

FIG. 1 illustrates a fastener driving tool 10 having a pneumatic motorassembly 15 which includes a cylinder 20 and a piston 25 slidablymounted within the cylinder. A novel snap-action valve assembly 30 asdescribed therein is used for controlling the motor assembly 15.Although the invention is described as embod ied in an improved fastenertool, it is to be understood that the motor assembly and valve areequally adaptable to many other applications; also, the describedfastener tool is exemplary of other tools with which the presentinvention can be used.

Fastener driving tool 10 includes a hollow housing 11 having a graspableelongated chamber portion 12 mounted on a base 13 at one end of portion12. The housing portion 12 defines therein a storage chamber 9. Housingll also includes an upright generally cylindrical portion 14 at theotherend thereof comprised of a lower body portion 42 that is closed atits lower end except for a central port 44, and a cap 43 for closing theupper end of the body portion 42. The storage chamber 9 is adaptable tocontain pressurized air and is coupled to any suitable source of suchair at the end adjacent base 13 through a hose and coupling means 16.

Open-ended motor cylinder is of a smaller diameter and length thanhousing portion 14 and is centrally disposed therein so that an annularchamber 17 is defined between the outer wall of cylinder 20 and theinner wall of housing portion 14. The lower edge 22 of cylinder 20 isclosed by the closed lower end of housing portion 42 except for port 44.The annular chamber 17 is filled with pressurized air by being in directcommunication with storage chamber 9. Cylinder 20 is of a height suchthat its upper edge 21 is positioned just below the upper end of housingportion 42 when installed. Housing portion 42 is flanged to provide anannular rim surface 45 adjacent cylinder edge 21.

Slidably mounted within cylinder 20 is piston 25 having upper and lowerends 26 and 27 and movable between cylinder ends 21 and 22. Piston 25may be biased upwardly toward end 21 by any suitable means such as aspring. Preferably, however, the piston 25 and cylinder 20 areconstructed so as to define chamber 61 supplied with pressurized airfrom chamber 17 via ports 48 in cylinder 20. The exposed area of thepiston upper end 26 in chamber 61 is greater than that of piston lowerend 27 in chamber 61 resulting in an unbalanced upper force thereon. Formore particular details of such a piston bias means, reference should bemade to the above-referenced Langas patent. Piston 25 is moveddownwardly to cylinder end 22 in opposition to its bias force bypressurized air from chamber 17, and is further provided with an axialpassage-way 24 extending between ends to exhaust such air through port44 after completion of the downward cycle, to allow the piston bias toreturn the piston to its upward position.

Carried at the lower end 27 of the piston is an elongated staple driver39 that extends vertically through the central port 44 and guide 40,that is part of the staple magazine assembly 41 secured to base 13 belowcylinder 20 and portion 12 at one side thereof. Magazine assembly 41holds staples in a row transversely to the path of driver 39 andsupplies staples serially under driver 39 into guide 40 to be drivenwhen piston 25 with driver 39 descends toward the lower edge 22 ofcylinder 20. For further details of a fastener driving tool, referenceshould be made to the above-referenced Langas patent.

In order to periodically admit pressurized air to drive the piston 25downwardly, novel snap-action valve assembly 30 is provided at the upperedge of the cylinder 20. Unlike prior valve expedients, valve assembly30 at once opens fully in a completely novel snap manner which providesan instantaneous large opening at cylinder end 21, so that pressurizedair enters into the cylinder without the loss of pressure, andconsequently of piston driving power and efficiency, which is inevitablewithout the novel valve assembly. The valve assembly is supported byhousing cylindrical portion 14 and includes a thin circular diaphragm 31having a diameter at least equal to that of the rim surface 45 ofcylindrical body portion 42. The diaphragm carries a rigid circularback-up plate 32 on one side, of a diameter equal to, or greater thanthe outside diameter of cylinder 20. A resilient flexible circular disc33 of a diameter equal to or preferably somewhat greater than theoutside diameter of cylinder 20 is carried on the other side ofdiaphragm 31. Preferably, disc 33 is of a plastic material, althoughother resilient materials will also serve. This element is highlyimportant to the snap" operation of the valve to create instantaneouslya large opening at the cylinder end. Specifically, the disc is used tomaintain a seal at cylinder end 21 while diaphragm 31 begins to moveaway from end 21 until finally snapping" away to present a largeopening, as will be described in greater detail. Both plate 32 and disc33 are secured to diaphragm 31 by a nut and bolt assembly 35 passedthrough the center of each member. In this manner the periphery of disc33 is not itself bound to diaphragm 31, a fact which is important forthe snap operation of disc 33, as will later be described.

Neither cylinder 20 together with piston 25, nor valve assembly 30, neednecessarily be of a round configuration; instead, for example, cylinder20 could well be a tubular member with a square or rectangular crosssection, and valve assembly 30 together with disc 33 of similar squareor rectangular cross section. Furthermore, it is not necessary in eitherthe round or rectangular configurations that the disc be fastened at itscen-' ter to the diaphragm 31, as-long as the disc is fastened inwardlyfrom at least one portion of the disc periphery and the disc may bemoved relative to the diaphragm.

The valve assembly 30 is placed over the annular rim surface 45 of theflanged end of portion 42 and with disc 33 overlapping and seating onedge 21. In this position, an outer generally annular portion 36 ofdiaphragm 31 overlies rim surface 45. The open end of cap 43 is alsoflanged to provide a second matching annular rim surface 46 adaptable tobe placed in registration over surface 45. Assembly 30 is secured withend housing portion 14 by clamping annular disc portion 36 between cap43 and housing portion 42, with the respective rims and annular portionhaving their centers in registration.

When thus properly positioned over cylinder edge 21 and secured withinhousing portion 44, the valve assembly divides the annularchamber'region 17 from an upper chamber 18 within cap 43 and above plate32. An intermediate annular portion 47 of diaphragm 31 bridges annularchamber 17 between cylinder 20 and housing portion 14 and is providedwith an annular, up-

wardly bulging convex bend 37, to allow the portion of diaphragmoverlying its cylinder 20 to be moved upwardly away from edge 21 fromits normal first position adjacent cylinder edge 21 to a second positionspaced therefrom, as is illustrated in FIG. 2.

It should be noted that the diaphragm 31 could instead be replaced by adifferent movable valve support member, for example, a piston or rigidplate slidably and sealingly mounted within housing portion 14 andsimilarly creating a chamber such as upper chamber 18 above such movablesupport member and an annular chamber such as chamber 17 below'it. Justas in the case of diaphragm 31, the member would be movable between aposition adjacent edge 21 to a position spaced therefrom. The resilientdisc 33 similarly would be attached to one surface of the member to sealthe cylinder at its upper end 21.

A downwardly acting biasing force must be provided for biasing valveassembly 30 toward the cylinder 20, and disc 33 into sealing engagementwith cylinder end 21, so that cylinder 20 is properly sealed off fromthe pression spring 19 in chamber 18 to insure that after the driver 39is driven and high-pressure air is introduced to chamber 18, the valveassembly 30 will be returned to sealing relationship with the cylinderend 21. The conduit28 is incorporated within'a portion of the wall ofboth cap 43 and housing portion 42 and extends generally verticallyadjacent housing portion 12. At its upper end, the conduit opens intochamber 18, while at its lower end, it opens into control valve 50,which is secured within housing portion 12 at a lower surface thereofand adjacent cylindrical housing portion 14.

Control valve 50 includes a central control chamber 51 into whichconduit 28 opens through its lower opening 52 and which houses a ball53. Also included is an inlet port 54 and an exhaust port 55 extendinggenerally vertically and respectively above and below control chamber51, with port 54 communicating with storage chamber 9, and exhaust port55' communicating with the outside atmosphere. A trigger assembly 57operates avalve plunger 58 having an end bearing on ball 53 to movetheball vertically from a first position wherein ball 53 seals exhaust port55 and opens inlet port 54, to a second position, wherein ball 53 sealsinlet port 53 and opens exhaust port 55.1

Normally ball 53 is at rest in the lower part of the chamber 51 in itsvfirst position. In this position, upper chamber 18 through conduit 28and valve 50 is'in communication with storage chamber 9 and thus issupplied with pressurized air. It will be remembered that the annularlower chamber 17 is in constant communication with the storage chamber 9and is therefore constantly supplied with the same pressurized air.Thus, the pressurized air inboth upper and lower chambers 18 and 17 actsrespectively on the upper and lower surfaces of valve assembly 30,setting up opposed downwardly and 'upwardly acting forces upon theassembly. However,

the air of the upper chamber 18 acts over the entire top surface of thevalve assembly, while theair in thelower chamber 17 acts only over theannular portion 47 of diaphragm 30, since this is the only portion ofthe lower surface of the valve which is exposed to pressurized air 'inchamber 17. The pressure due to the air in chamber 18 then acts over amuch larger area than the pressure due to chamber 17, thereby providinga large resulting downward force acting to force valve assembly 30towards a cylinder and bias disc 33 into sealing engagement with upperedge 21 of cylinder 20, as well as isolate cylinder 20 from chamber 17.This is the position of the valve assembly 30 which is illustrated inFIG. I.

It should be noted that a resulting downward force could also beproduced even in the absence of a differential area in favor of theupper surface of valve assembly'30 by simply supplying chamber l8-withair of correspondingly higher pressure, or even as previously indicated,by a relatively strong spring and release mechamsm. 1

The tool may then be operated by upwardly moving i trigger assembly 57to drive plunger 58 and move ball 53 upwardly and preferably onlymomentarily to seal port 54 and open exhaust port 55, to vent chamber 18through conduit 28 and port 55 to the atmosphere. As the air pressure inchamber 18 decreases, the resulting force on the annular portion 47 ofthe diaphragm becomes essentially that due to the air pressure inchamber 17, which moves the diaphragm 31 upwardly to its spaced secondposition. Although such air pressure reduction in chamber 18 appears tobe instantaneous insofar as operation of the tool is concerned, itactually exhibits a finite time gradient which enables the air pressurein chamber 17 to act between disc 33 and diaphragm 31 to bias theperiphery of the disc 33 downwardly into sealing engagement with thecylinder edge 21, even as diaphragm 31 is being moved upwardly to itsspacedposition. In this manner, the opening of cylinder 20 topressurized air is delayed until diaphragm 31 (or other valve supportmember) is moved upwardly to its spaced second position.

is finally broken, the remainder of the valve assembly has had time tobecome well-separated from cylinder 20, so that the opening to thecylinder for the pressurized air when finally effectedvwill be asubstantial one. Equally importantly, the opening is madeinstantaneously by the disc finally snapping away from cylinder 20 to aposition flat against diaphragm 31 as will be described. It is importantto note that such'disc operation only may be achieved if the manner offastening disc 33 not only permits it to move relative to diaphragm 31,but also leaves at least much of the periphery of the disc unfastened sothat the air pressure inchamber 17 may act to bias this peripheryagainst edge 21. The reason for the requirement that the disc befastened inwardlyof at least one portion of its periphery, andpreferablyat its center, should now be clear.

The configuration of the valve assembly just prior to the instant whenit opens is illustrated by FIG. 2. Of

course, since disc 33 is attached atits center to diaphragm 31, thecenter of the disc is moved upwardly with diaphragm 31 even as theperiphery of the disc is being forced downward against edge 21. The discthereby becomes distorted into a convex or cone-like configuration,illustrated by FIG. 2. Due to the resiliency of the disc, a restoringforce is built up within the disc as thedistortion of the discincreases, which tends to cause the disc to return to its normally flatshape. Finally, as the air pressure in the chamber 18 becomesatmospheric pressure and the diaphragm under the influence of chamber 17air pressure reaches its second position spaced from cylinder edge 21,the restoring force due to the resiliency of the disc overcomes theforce of air pressure acting downwardly on the disc periphery. The discsnaps away from the cylinder to its original flat shape against thelower surface of the diaphragm 31 (see FIG. 3), which is in its spacedsecond position away from cylinder 20. A large annular openin'g betweencylinder 20 and pressurized chamber 17 is thus instantaneously created,allowing the highly pressurized air of chamber 17 to rush insidecylinder 20 substantially with a minimum drop of pressure. The air,

acting upon the upper surface of piston 25 overcomes the upward bias ofthe piston to drive it instantaneously downward, along with driver 26and an associated staple supplied by magazine assembly 41 to guide 40immediately therebelow.

In the meantime, as trigger assembly 57 is moved to the end of itsupward stroke, it allows plunger 58 and ball 53 to descend to theiroriginal positions, wherein ball 53 closes off exhaust port 55 and opensinput port 54, the trigger assembly thereafter returning to its originalposition upon being released by the operator. With the opening of port54, pressurized air from storage chamber 9 then again passes throughopening 52 and conduit 28 into upper chamber 18, so that along with thespring 19, there exists a net downward force on valve assembly 30. Theresultant downward force biases diaphragm 31 to its formercylinder-adjacent first position while carrying disc 33 into sealingengagement with cylinder edge 22 to cut off pressurized air to cylinder20. It should be obvious at this point that any alternative controlvalve and conduit arrangement which also selectively suppliedpressurized air to upper chamber 18, as well as releasing it uponcommand, would also serve and that control valve 50 and conduit 28 aremerely exemplary.

The pressurized air in the cylinder escapes through axial passageway 24in piston 25 and port 44 at the lower end of housing portion 42. A widechoice of other means of exhausting such air may alternatively be used,since the action of the valve assembly is so rapid in subjecting piston25 to the full pressure of the air in chamber 17 that the loss ofdriving power through any of such exhaust expedients is negligible. Oncecylinder 20 is again sealed by valve assembly 30, the piston 25 isrestored to its normal upper position adjacent cylinder edge 21 asdescribed above to await the next driving cycle of the tool.

It will be appreciated that the improved valve assembly for the fluidmotor provides a substantial increase in efficiency, driving force, andspeed of operation at any given operating air pressure in comparisonwith prior-art expedients. This is because the cylinder is kept sealedagainst the air pressure for driving the piston even as some elements ofthe valve assembly begin to move away from the cylinder, until thesealing disc is able to snap at once to a position spaced well away fromthe cylinder. Thereupon a large opening is instantaneously available forthe passage of pressurized air into the cylinder, and thus the maximumavailable air pressure is brought to bear to drive the piston with aminimum loss of available air pressure. Consumption of air by devicessuch as the fastener tool is lowered, and their power is increased, withstaples being driven more forcefully for improved penetration. Ofcourse, as was earlier stated, the improved motor and valve may be usedin any related tool application, or indeed in any application callingfor the use of such a motor. Neither is the invention limited to airpowered applications, since it is also adaptable to work with otherappropriate fluids.

What is claimed is:

l. A valve system for controlling the flow of fluid under pressure to afluid motor located in a tubular member, said system comprising: ahousing, a tubular member positioned in said housing; a fluid motorlocated in said tubular member; a diaphragm valve support member movablysupported in said housing adjacent an open end of the tubular member andhaving a first surface for moving toward said open end and defining anarea outwardly of such end exposed to said fluid contained underpressure in said housing, said support member also defining a secondsurface opposite said first surface, said first surface outer area beingsubjected to a first biasing force due to said pressurized fluid in saidhousing tending to bias said support member away from the open end ofthe tubular member, said second surface being subjected to a secondbiasing force acting in opposition to said first biasing force; aresilient disc positioned in said housing to overlie and to close saidopen end, said disc terminating inwardly of the peripheral edge of saidsupport member; means securing said disc to said first support surfaceinwardly of at least a portion of the disc periphery whereby said discperiphery is movable relative to said first support surface and relativeto the portion of said disc secured to said first support surface, saidsupport member biasing said disc into sealing engagement with said openend of said tubular member due to said second biasing force; and controlmeans operable for releasing at least a portion of said second biasingforce to allow said pressurized fluid in said housing to move said firstsupport surface away from said open end while initially maintaining saidresilient disc in sealing engagement with said open end, said resilientdisc finally snapping away from said open end when the support memberhas become spaced from said tubular member, thereby instantaneouslyopening a large aperture to said open end of said tubular member toexpose the tubular member to said pressurized fluid in said housingwhereby said pressurized fluid may enter said tubular member throughsaid open end to drive said fluid motor.

2. A valve system as in claim 1 in which said second surface is exposedto said fluid under pressure, and said control means for releasing atleast a portion of said second biasing force includes a control valvecontrolling the application of said pressurized fluid to said secondsurface.

3. A valve system as in claim 1 in which said support member issupported upon an inner wall of said housing and divides said housinginto a first chamber confronting said second surface and a secondchamber about said tubular member said second chamber being continuouslysupplied with said pressurized fluid to furnish said first biasingforce.

4. A valve system as in claim 3 in which said first chamber is alsosupplied with pressurized fluid to subject said second surface topressure and thereby to provide at least a portion of said secondbiasing force and said control means is operable to cut off saidpressurized fluid to said first chamber to thereby release at least aportion of said second biasing force.

5. A valve system as in claim 4 in which said fluid is air, and saidcontrol means includes a valve selectively connecting said first chamberto the atmosphere for releasing said pressurized air therein, and to asource of pressurized air for again supplying pressurized air to saidfirst chamber.

6. A valve system as in claim 4 in which said first surface outer areaextends between the inner wall of said housing and the outer wall ofsaid tubular member and is generally annular in configuration.

7. A valve system as in claim 4 in which said resilient disc issubstantially congruent with the open end of said tubular member.

8. A pneumatically operated fastener driving tool comprising: a housingadapted to contain air under pressure; a tubular member disposed withinsaid hous- 9 ing and having an open end for exposure to said pressurizedair; a piston slidably mounted within the tubular member and normallybiased toward said open end, said piston being provided with a fastenerdriver on one side thereof opposite the side facing said open end; aclosure member supported within said housing and positioned to extendacross said open end and having a periphery engaging said housing, saidclosure member being movable between an open position spaced from saidopen end and a closed position adjacent said open end, said closuremember having a first surface facing towards said open end and anopposite surface facing away from said open end, said closure memberdividing said housing into a storage chamber on said first surface sidemaintaining pressurized air over said first surface, and an operatingchamber on said opposite surface side, a compression spring in saidoperating chamber acting on said opposite surface, said storage chambercontaining pressurized air providing a first force upon said firstsurface tending to move said closure member away from said open end; aresilient disc secured to said first closure member surface at alocation inwardly of the periphery of said disc and sealingly engageablewith said cylinder open end; control means for selectively admitting andexhausting pressurized air to said operating Chamber, said air uponadmittance providing a second force acting in conjunction with saidcompression spring to overcome said first force to bias said closuremember toward said closed position and said disc into sealing engagementwith said open end, said means thereafter exhausting said operatingchamber to allow said closure member to move from said closed positionto said open position under the influence of said first force, with saidresilient disc initially maintaining sealing engagement with said openend under the influence of pressurized air admitted between said discand said support member from said storage chamber, said disc finallysnappingaway from said open end against and toward said one closuremember surface, thereby instantaneously opening said open end to saidstorage chamber pressurized air to drive said piston together with saidfastener driver, said means thereafter again admitting pressurized airto said operating chamber to again seal said open end; and means forventing the air confined between said resilient disc and said pistonwhen said disc is restored to scaling engagement with said open end,allowing said piston bias to return said piston to its original positionnear said open end.

1. A valve system for controlling the flow of fluid under pressure to afluid motor located in a tubular member, said system comprising: ahousing, a tubular member positioned in said housing; a fluid motorlocated in said tubular member; a diaphragm valve support member movablysupported in said housing adjacent an open end of the tubular member andhaving a first surface for moving toward said open end and defining anarea outwardly of such end exposed to said fluid contained underpressure in said housing, said support member also defining a secondsurface opposite said first surface, said first surface outer area beingsubjected to a first biasing force due to said pressurized fluid in saidhousing tending to bias said support member away from the open end ofthe tubular member, said second surface being subjected to a secondbiasing force acting in opposition to said first biasing force; aresilient disc positioned in said housing to overlie and to close saidopen end, said disc terminating inwardly of the peripheral edge of saidsupport member; means securing said disc to said first support surfaceinwardly of at least a portion of the disc periphery whereby said discperiphery is movable relative to said first support surface and relativeto the portion of said disc secured to said first support surface, saidsupport member biasing said disc into sealing engagement with said openend of said tubular member due to said second biasing force; and controlmeans operable for releasing at least a portion of said second biasingforce to allow said pressurized fluid in said housing to move said firstsupport surface away from said open end while initially maintaining saidresilient disc in sealing engagement with said open end, said resilientdisc finally snapping away from said open end when the support memberhas become spaced from said tubular member, thereby instantaneouslyopening a large aperture to said open end of said tubular member toexpose the tubular member to said pressurized fluid in said housingwhereby said pressurized fluid may enter said tubular member throughsaid open end to drive said fluid motor.
 2. A valve system as in claim 1in which said second surface is exposed to said fluid under pressure,and said control means for releasing at least a portion of said secondbiasing force includes a control valve controlling the application ofsaid pressurized fluid to said second surface.
 3. A valve system as inclaim 1 in which said support member is supported upon an inner wall ofsaid housing and divides said housing into a first chamber confrontingsaid second surface and a second chamber about said tubular member saidsecond chamber being continuously supplied with said pressurized fluidto furnish said first biasing force.
 4. A valve system as in claim 3 inwhich said first chamber is also supplied with pressurized fluid tosubject said second surface to pressure and thereby to provide at leasta portion of said second biasing force and said control means isoperable to cut off said pressurized fluid to said first chamber tothereby release at least a portion of said second biasing force.
 5. Avalve system as in claim 4 in which said fluid is air, and said controlmeans includes a valve selectively connecting said first chamber to theatmosphere for releasing said pressurized air therein, and to a sourceof pressurized air for again supplying pressurized air to said firstchamber.
 6. A valve system as in claim 4 in which said first surfaceouter area extends between the inner wall of said housing and the outerwall of said tubular member and is generally annular in configuration.7. A valve system as in claim 4 in which said resilient disc issubstantially congruent with the open end of said tubular member.
 8. Apneumatically operated fastener driving tool comprising: a housingadapted to contain air under pressure; a tubular member disposed withinsaid housing and having an open end for exposure to said pressurizedair; a piston slidably mounted within the tubular member and normallybiased toward said open end, said piston being provided with a fastenerdriver on one side thereof opposite the side facing said open end; aclosure member supported within said housing and positioned to extendacross said open end and having a periphery engaging said housing, saidclosure member being movable between an open position spaced from saidopen end and a closed position adjacent said open end, said closuremember having a first surface facing towards said open end and anopposite surface facing away from said open end, said closure memberdividing said housing into a storage chamber on said first surface sidemaintaining pressurized air over said first surface, and an operatingchamber on said opposite surface side, a compression spring in saidoperating chamber acting on said opposite surface, said storage chambercontaining pressurized air providing a first force upon said firstsurface tending to move said closure member away from said open end; aresilient disc secured to said first closure member surface at alocation inwardly of the periphery of said disc and sealingly engageablewith said cylinder open end; control means for selectively admitting andexhausting pressurized air to said operating chamber, said air uponadmittance providing a second force acting in conjunction with saidcompression spring to overcome said first force to bias said closuremember toward said closed position and said disc into sealing engagementwith said open end, said means thereafter exhausting said operatingchamber to allow said closure member to move from said closed positionto said open position under the influence of said first force, with saidresilient disc initially maintaining sealing engagement with said openend under the influence of pressurized air admitted between said discand said support member from said storage chamber, said disc finallysnapping away from said open end against and toward said one closuremember surface, thereby instantaneously opening said open end to saidstorage chamber pressurized air to drive said piston together with saidfastener driver, said means thereafter again admitting pressurized airTo said operating chamber to again seal said open end; and means forventing the air confined between said resilient disc and said pistonwhen said disc is restored to sealing engagement with said open end,allowing said piston bias to return said piston to its original positionnear said open end.